ES2554769T3 - Printhead set, method and screen printing system - Google Patents

Abstract

A print head assembly for printing a print medium on a workpiece through a print screen (105) that includes a screen element (109) having a pattern of print openings (110) therein , wherein the assembly comprises first and second printhead units (143, 145) that are mounted in parallel relationship adjacent to, and between, first and second carriages (141, 141), and wherein each of the units of printhead (143, 145) comprises first and second drive devices (147, 147) of printhead that can be mounted on the respective carriages (141, 141), and a support member (151) that is extends between the printhead drive devices (147, 147), such as to be movable vertically therebetween, and in use supports a printing element (181, 183), the support members (151) of the printhead units (143 , 145) arranged in spaced relationship, such as to allow the introduction of print media from above between them.

Description

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DESCRIPTION

Printhead set, method and screen printing system

The present invention relates to a printhead assembly for printing a printing medium, such as a fluid ink or a soft solder paste, on workpieces, including flexible or delicate substrates, for example, such as those used in applications of fuel or solar cells, through a print screen that includes a pattern of print openings corresponding to a pattern of deposits to be printed on a workpiece, a screen printing system that incorporates the same and screen printing method.

Many systems and serigraph print heads have been developed for printing media in workpieces.

Figures 1 and 2 illustrate a typical screen printing system using a print head in the form of a strip.

The screen printing system comprises a rigid support frame 3, which supports a print screen 5, a pair of spaced parallel linear supports 7, 7 that are mounted to support the support frame 3 on opposite sides of the print screen 5, a print carriage 9 that includes a portico 11 that is supported on the linear supports 7, 7, and a print head assembly 15 that is mounted on the portico 11 and can function to print a print medium through a pattern of print openings in the print screen 5 on a workpiece that is supported beneath it, and a pulse unit 17, comprising a drive motor 19 and a toothed pulse belt 21 that is coupled to the print carriage 9, to drive in vaiven the printing carriage 9 along the linear supports 7, 7.

The printhead assembly 15 comprises first and second strips 23, 25, which are juxtaposed in parallel relationship and are movable vertically independently in order to allow configuration depending on the direction of printing, and an impulse mechanism 27 that It attaches the strips 23, 25 to the portico 11 by means of a spring coupling (not illustrated) and can work vertically to raise and lower the strips 23, 25 and maintain a downward force in the operation of the strips 23, 25. The mechanism Pulse 27 comprises first and second drive devices 31, 33, aqrn stepper motors coupled by spindles, which can operate vertically to raise and lower the respective ones of the strips 23, 25.

The operation of the printhead assembly 15 is illustrated in Figures 2 (a) and (b). As illustrated in Fig. 2 (a), when the printing is in a first direction D1 with the first strip 23, the first drive device 31 is operated to drive the first strip 23 downwards until contact with the screen of impression 5 and raising the impulse mechanism 27 against the predisposition of the spring coupling, so that a predetermined downward predisposition force is applied to the first strip 23, and a second drive device 33 functions to drive the second strip 25 towards above, so that the lower edge of the second strip 25 is raised by separating it from the face of the first strip 23 in order to allow a space for separation forward of the first strip 23 in the first direction of impression D1, which is necessary to allow the printing medium to roll in front of the first strip 23. Similarly, as illustrated in Figure 2 (b), when the printing is in the other second direction D2 with the second strip 25, the second drive device 33 functions to drive the second strip 25 down to the contact with the printing screen 5 and raise the impulse mechanism 27 against the predisposition of the spring coupling, so that it is applied a predetermined downward predisposing force to the second strip 25, and a first drive device 31 functions to drive the first strip 23 upward, so that the lower edge of the first strip 23 is raised separating it from the face of the second strip 25 in order to allow a separation space forward of the second strip 25 in the second direction of printing D2, which is necessary to allow the print medium to roll in front of the second strip 25.

This screen printing system has worked very successfully, but the present inventor has recognized that this screen printing system suffers several drawbacks, particularly in relation to the printing of fluid inks on flexible and delicate workpieces. In particular, the volume of the portico 11, which is necessary to confer the necessary stiffness, and the weight of the impulse mechanism 27 that is mounted in the portico 11, limit the speed of movement of the printhead assembly 15 and therefore the machine productivity, and also induce vibrations at the beginning and at the end of each printing run, these vibrations are particularly harmful in relation to the printing of fluid inks on flexible and delicate workpieces. In addition, the volume of the portico 11 restricts the vision of the print screen 5.

Also included printheads included. Examples include the applicant's previous documents WO-A-1998/016387 and WO-A-2001/005592, in which these silk screen heads are sold under the ProFlow (RTM) brand.

The included printheads have worked very successfully to date, particularly in the printing of solder pastes on printed circuit boards, but the new applications, particularly in the production of fuel cells and solar cells, which use flexible and delicate substrates Y

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they require the printing of fluid inks, they have needs that these existing screen printing heads cannot meet.

EP-A-0806295 describes a compressed air scraper blade assembly for printing stations.

US-A-4586433 describes a screen printing apparatus that includes a print carriage assembly having a countertop, a print strip and an excess ink strip.

WO-A-1997/008655 describes a screen printing apparatus that includes a pair of strips that can be raised or lowered.

WO-A-2006/100116 describes a screen printing machine that includes a printing frame and a carrier structure, which allows the printing frame to be raised or lowered with respect to a printing plane.

Thus, a goal of the present invention is to provide an alternative printhead assembly for printing a print medium on work pieces, which at least in one embodiment allows the printing of flexible and delicate workpieces and also allows the printing of fluid printing media, such as liquid inks.

In one aspect the present invention provides a print head assembly for printing a printing medium on a workpiece through a printing screen that includes a screen element having a pattern of print openings therein, characterized because the assembly comprises first and second printhead units that are mounted in parallel relationship adjacent to, and between, the first and second carriages, wherein each of the printhead units comprises first and second drive devices of printhead that can be mounted on the respective carriages, and a support member that extends between the printhead drive devices, such as to be movable vertically thereon, and in use supports a print element , the support members of the printhead units being arranged in spaced relationship, such as to allow the in Print media printing from above between them.

In one embodiment the rods comprise horizontal rods, preferably linear supports.

In one embodiment, the printhead drive devices of each printhead unit can function to provide a controlled downward force to the respective support member, thereby allowing the application of a controlled downward force to a printing element. when connected to the support member.

In one embodiment the controlled downward force is in the range of 0 to about 15 N, preferably with an accuracy of less than about 1%.

In one embodiment, the printhead drive devices comprise low friction drive devices.

In one embodiment, the printhead drive devices comprise low friction pneumatic drive devices.

In one embodiment, each of the printhead drive devices comprises a cylinder, a floating piston that is movably disposed within the cylinder and includes a connection element that is connected to one end of the support member, and at least a fluid orifice to which fluid pressure is applied to raise or lower the floating piston.

In one embodiment each of the printhead units comprises vertical grains, preferably linear supports, which grind the respective support member vertically, so that substantially no horizontal force component is transmitted to the respective printhead drive devices .

In one embodiment, the support member comprises a substantially U-shaped member.

In one embodiment, the U-shaped support member defines a substantially cleared opening when viewed laterally.

In one embodiment, the support member includes first and second support elements that engage the respective of the first and second printhead drive devices and extend vertically adjacent to respective inner sides of the printhead drive devices , and a horizontal bar element that extends between opposite lower ends of the support elements.

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In one embodiment, each of the printhead units comprises a stop adjustment mechanism, which allows setting upper and lower limits for the vertical movement of the respective printhead drive devices.

In one embodiment, the stop adjustment mechanism comprises first and second stop adjusters, preferably screw adjusters, at each end of the support member, the first stop adjusters establishing a lower limit for the vertical movement of the respective drive actuators. printhead and by setting the second stop adjusters a superior function for vertical movement of the respective printhead drive devices.

In one embodiment, the second stop adjusters can be decoupled to allow the respective support member to be lifted very far from the print screen, thereby facilitating the removal of the print screen.

In one embodiment, the support member of the first printhead unit has a strip blade connected thereto and the support member of the second printhead unit has a counter-strip connected thereto, and the assembly is movable in strokes. of impression and return directed opposite, so that, in the race of impressesion, the devices of impressesion of head of impressesion of the first unit of impressesion head are controlled to take the strip of strip to the operative contact with the element of screen and apply to it a downward force necessary for printing and the printhead drive devices of the second printhead unit are controlled to raise the counter-rail to an inoperative position, and, in the return stroke, the Print head drive of the first print head unit are controlled to raise the blade blade to a The inoperative position and the printhead actuation devices of the second printhead unit are controlled to lower the countertop to an operating position slightly separated from the screen element, such as to allow the application of a print media film. on the surface of the screen element.

In another embodiment, each of the support members of the printhead units has a strip blade connected thereto, and the assembly is movable in first and second print races directed opposite, so that, in the first race of printing, the printhead drive devices of the first printhead unit are controlled to bring the strip blade connected thereto to the operative contact with the screen element and apply to it a downward force necessary to print and the printhead drive devices of the second printhead unit are controlled to raise the strip connected to the same second print stroke of the screen element, and, in the second print stroke, the devices The print head drive of the first print head unit is controlled to raise the strut blade co they are connected to a position slightly separated from the screen element and the print head drive devices of the second print head unit are controlled to lower the strip terminal connected thereto to the operative contact with the screen element and apply to it a downward force necessary to print.

In another aspect, the present invention provides a screen printing system, comprising: a support frame that supports a printing screen and includes first and second grains, optionally the support frame has a rectangular shape in plan view and includes support elements first and second frame on each of the opposite sides thereof that receive and support the opposite sides of the print screen; the assembly described above that is supported on and between the grids, such as to be movable to print a print medium through the print screen on a work piece that is supported under it; and a unit of impulse to drive the assembly along the cranes in one of the first and second opposite directions.

In one embodiment, the support frame has a rectangular shape in plan view and includes first and second frame support elements on each of the opposite sides thereof that receive and support the opposite sides of the print screen.

In a further aspect the present invention provides a screen printing method of a printing medium on a workpiece through a printing screen that includes a screen element having a pattern of print openings therein, the method comprising the steps of: providing a printhead assembly comprising: first and second carriages that are movably supported in the respective first and second grilles; characterized in that the printhead assembly further comprises: first and second printhead units that are mounted in parallel relationship adjacent to, and between, the carriages, wherein each of the printhead units comprises drive devices first and second of the printhead that can be mounted on the respective of the carriages, and a support member that extends between the printhead drive devices, such as to be movable vertically therebetween, the members of support of printhead units arranged in spaced relationship; connect impression elements, such as one of a power strip or

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a counter-board, to the support members of the printhead units; introduce print media from above and between support members; and put into operation the assembly for printing on a work piece that is supported under the printing screen.

In one embodiment, the ranges comprise horizontal ranges, preferably linear supports.

In one embodiment, the printhead drive devices of each printhead unit can function to provide a controlled downward force to the respective support member, thereby allowing the application of a controlled downward force to the printing element that is connected to the support member.

In one embodiment the controlled downward force is in the range of 0 to about 15 N, preferably with an accuracy of less than about 1%.

In one embodiment, the printhead drive devices comprise low friction drive devices.

In one embodiment, the printhead drive devices comprise low friction pneumatic drive devices.

In one embodiment, each of the printhead drive devices comprises a cylinder, a floating piston that is movably disposed within the cylinder and includes a connection element that is connected to one end of the support member, and at least a fluid orifice to which fluid pressure is applied to raise or lower the floating piston.

In one embodiment, each of the printhead units comprises vertical ranges, preferably linear supports, which the respective support member vertically rotates, so that substantially no horizontal force component is transmitted to the respective printhead drive devices .

In one embodiment, the support member comprises a substantially U-shaped member.

In one embodiment, the U-shaped member defines a substantially cleared opening when viewed laterally.

In one embodiment, the support member includes first and second support elements that engage the respective of the first and second printhead drive devices and extend vertically adjacent to respective inner sides of the printhead drive devices , and a horizontal bar element that extends between opposite lower ends of the support elements.

In one embodiment each of the printhead units comprises a stop adjustment mechanism, which allows setting upper and lower limits for the vertical movement of the respective printhead drive devices.

In one embodiment, the stop adjustment mechanism comprises first and second stop adjusters, preferably screw adjusters, at each end of the support member, and the method further comprises the step of: adjusting the first stop adjusters to establish a lower limit. for the vertical movement of the respective printhead drive devices and the second stop adjusters to establish an upper limit for the vertical movement of the respective print stop adjusters.

In one embodiment, the method further comprises the step of: decoupling the second stop adjusters to allow the respective support member to be lifted away from the print screen, thereby facilitating the removal of the print screen.

In one embodiment, the method further comprises the step of: introducing print media from above and between the support members.

In one embodiment, the support member of the first printhead unit has a strip blade connected thereto and the support member of the second printhead unit has a counter-strip connected thereto, and the operation stage of the assembly The print head comprises the steps of: controlling the print head drive devices of the first print head unit to bring the strip blade to the operative contact with the screen element and apply a necessary downward force thereto to print; control the printhead drive devices of the second printhead unit to raise the counter-board to an inoperative position; propelling the assembly on the surface of the screen element in a first direction to print deposits of the printing medium on the workpiece that is supported under the printing screen; control the printhead drive devices of the first printhead unit to raise the blade blade to a position

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inoperative; controlling the printhead drive devices of the second printhead unit to lower the counterscreen to an operating position slightly separated from the screen element; and propelling the assembly on the surface of the screen element in a second opposite direction to apply a film of printing medium on the surface of the screen element.

In another embodiment, each of the support members of the first and second printhead units has a strip blade connected thereto which together define a cavity, and the operating stage of the printhead assembly comprises the steps of : control the printhead drive devices of the first printhead unit to bring the strip blade connected thereto to the operative contact with the display element and apply to it a downward force necessary to print; control the printhead drive devices of the second printhead unit to raise the strip connected to them slightly separated from the screen element; propelling the assembly on the surface of the screen element in a first direction to print deposits of the printing medium on the workpiece that is supported under the printing screen; controlling the printhead drive devices of the first printhead unit to raise the strip connected to them to a position slightly separated from the screen element; controlling the printhead drive devices of the second printhead unit to lower the strip blade connected thereto to the operative contact with the display element and apply to it a downward force necessary to print; and propelling the assembly on the surface of the screen element in a second opposite direction to print deposits of the printing medium on the workpiece that is supported under the printing screen.

In one embodiment, the method further comprises the step of: maintaining the cavity between the paddle blades with a volume of printing medium that is such that the printing medium extends at least through the cavity in contact with each of the the paddle blades.

In another embodiment, the method further comprises the step of: keeping the cavity between the strip blades substantially filled with printing medium.

In one embodiment the printing medium is a fluid material, preferably a liquid ink.

In another embodiment the printing medium is a thick viscous material, preferably a soft solder paste.

Preferred embodiments of the present invention will now be described, later in this specification, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 illustrates a perspective view of the prior art screen printing system;

Figures 2 (a) and (b) illustrate the operation of the printhead assembly of the screen printing system of Figure 1 in first and second opposite print strokes;

Figure 3 illustrates a perspective view of a screen printing system according to a preferred embodiment of the present invention;

Figure 4 illustrates a first vertical sectional view (along section I-I in Figure 3) of the screen printing system of Figure 3;

Figure 5 illustrates a second vertical section view (along section M-M in Figure 3) of the screen printing system of Figure 3;

Figures 6 (a) and (b) illustrate the operation of the printhead assembly of the screen printing system of Figure 3 in a first printing stroke and a second return stroke, respectively; Y

Figures 7 (a) and (b) illustrate the operation of the print head assembly of an alternative embodiment of the screen printing system of Figure 3 in first and second opposite print strokes, respectively.

Figures 3 to 6 illustrate a screen printing system according to a preferred embodiment of the present invention, which is configured to receive a print screen 105 and print on work pieces through the print screen 105.

In this embodiment, the printing screen 105 comprises a frame 107, which is rectangular in plan view, and a screen element 109, still in the form of a solid sheet, either formed of metal or plastic material, or a coated mesh, which is mounted with tension on the frame 107 and includes a pattern of print openings 110, which defines a printing area, through which a print medium is printed on a workpiece supported under it.

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The screen printing system comprises a nested support frame 111 that supports the printing screen 105, first and second horizontal ranges 117, 117 that are arranged in parallel relationship on the support frame 111 on opposite sides of the print screen 105, a printhead assembly 119 that is supported in horizontal ranges 117, 117 such as to be movable in a horizontal plane and print a print medium through print screen 105 on a workpiece that is supported below the same, and a pulse unit 121 for driving the printhead assembly 119 along the horizontal ranges 117, 117 in one of the first and second opposite directions D1, D2.

In this embodiment, the support frame 111 has a rectangular shape in plan view and includes first and second frame support elements 125, 125, aqm projections, on opposite sides thereof, aqm on the lower edges, which receive and they support the opposite sides of the frame 107 of the printing screen 105.

In this embodiment, as illustrated in Figure 5, the opposite sides of the support frame 111 include inwardly oriented positioning elements 131, which act to locate the print screen 105 within the support frame 111. In this embodiment the elements of location 131 on one side of the support frame 111 are resiliently arranged, here by means of spring elements 133, such as to predispose the frame of the printing screen 105 against the location elements 131 on the other side of the support frame 111.

In this embodiment, the screen printing system further comprises a screen lock mechanism 135 for locking the print screen 105 in a fixed position in the support frame 111.

In this embodiment, as illustrated in Figure 5, the screen lock mechanism 135 comprises a plurality of clamp members 137 that are arranged in opposite relation to the frame support members 125, 125 and can function to hold the frame 107 of the printing screen 105 in the frame support elements 125, 125, and at least one, in this embodiment a plurality of actuating devices 139, aqm pneumatic actuating devices, for moving the clamp members 137 to hold the print screen 105 in support frame 111.

In this embodiment the horizontal ranges 117, 117 in the support frame 111 comprise linear supports on which opposite ends of the printhead assembly 119 are movably supported.

In this embodiment, the printhead assembly 119 comprises first and second carriages 141, 141, which are mounted in the respective first and second horizontal ranges 117, 117, and first and second printhead units 143, 145, which they are mounted in parallel parallel relationship to and between the first and second cars 141, 141.

In this embodiment each of the first and second carriages 141, 141 includes a coupling element 142, including here a toothed section, for coupling to respective pulse elements 185, 185 of the pulse unit 121, as will be described more detail later.

Each of the printhead units 143, 145 comprises first and second drive devices 147, 147 of printhead that are mounted on the respective of the first and second carriages 141, 141, a support member 151 extending between the print head actuator devices 147, 147, such as to be movable vertically thereon, and to support a printing element, either as a strip blade 181 or a bar / counter plate 183, as will be described more detail below, and first and second vertical ranges 152, 152, which support support member 151 in a vertical orientation.

By supporting the printhead drive devices 147, 147 directly on the support frame 111, and not in a necessarily bulky portico as in the prior art, the support members 151, 151 of the first print head units and Second 143, 145 can be very small in size, which also reduces the weight and also allows the support members 151, 151 to be located near the printing screen 105 and not extend over a significant height, here they have a height that is lower than the upper surface of the support frame 111, which improves visibility in the vision line. In this embodiment the support members 151, 151 have a substantially open section between the support frame 111 when viewed horizontally.

In this embodiment, the printhead drive devices 147, 147 comprise low friction pneumatic drive devices (type MQQ TB 20-10D, manufactured by SMC Pneumatics (RU), Milton Keynes, United Kingdom), which comprises a cylinder 153 , a floating piston 154 that is movably disposed within the cylinder 153 and includes a rod of rod 155 that extends vertically from the cylinder 153 and is moved by the movement of the floating piston 154, and first and second fluid holes 157, 159 to which fluid pressure is applied, here a pneumatic pressure, such as one of a positive pressure or a negative (empty) pressure, to raise or lower the floating piston 154 and the gma of vertically extended rod 155.

In this embodiment the respective of the first and second fluid holes 157, 159 of the printhead actuator devices 147, 147 of the respective of the printhead units

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first and second 143, 145 are commonly coupled, so that the printhead drive devices 147, 147 of the respective first and second printhead units 143, 145 operate at the same time.

In this embodiment the fluid supply is a pneumatic supply of compressed air which is delivered in a commuted manner to the first and second fluid holes 157, 159 of the printhead actuator devices 147, 147 of the respective units of the First and second printhead 143, 145 through a precision pressure regulator (type ITV1050 manufactured by SMC Pneumatics (RU), Milton Keynes, United Kingdom).

In this embodiment, the first and second vertical grains 152, 152 comprise linear supports on which movable ends of opposite support member 151 are movably supported, such as to ensure that no horizontal force component is transmitted to the actuating devices 147, 147 of the printhead, which otherwise acts to provide frictional resistance to the drive devices 147, 147 of the printhead, which impairs the necessary precision pressure control of the drive devices 147, 147 of the printhead Print.

In this embodiment, the support member 151 comprises a substantially U-shaped member, which includes first and second support elements 161, 161 which are coupled to the respective of the print head actuator devices 147, 147 and extend vertically adjacent to respective inner sides of the printhead actuator devices 147, 147, and a horizontal bar element 163 extending between opposite lower ends of the support elements 161, 161.

With this configuration, the U-shaped profile of the support members 151, 151 of the first and second printing units 143, 145 provides an operator with a much improved visibility of the surface of the printing screen 105, which is particularly advantageous for monitoring the state of the printing screen 105 and the printing medium.

In this embodiment each of the first and second printhead units 143, 145 comprises a stop adjustment mechanism 171, which allows setting upper and lower limits for the movement of the pistons 154, 154 of the drive devices 147, 147 printhead.

In this embodiment the stop adjustment mechanism 171 comprises first and second screw stop adjusters 173, 175, at each end of the support member 151, the first screw adjusters 173, 173 establishing a lower limit for the movement of the pistons 154, 154 of the printhead drive devices 147, 147 and the second screw adjusters 175, 175 establishing an upper limit for the movement of the pistons 154, 154 of the printhead drive devices 147, 147.

In one embodiment, the printhead drive devices 147, 147 can be provided as long drive devices, which, by decoupling the second upper limit screw adjusters 175, 175, allowed the respective support member 151 and the print element connected thereto are raised far apart from the print screen 105, thereby facilitating the removal of the print screen 105.

In this embodiment, the support member 151 of the first printhead unit 143 has a strip blade 181 connected thereto and the support member 151 of the second printhead unit 145 has a counter-strip 183 connected thereto.

Without pressure applied to the print head drive devices 147, 147 of the first print head unit 143, the strip blade 181 will rest on the surface of the screen element 109 of the print screen 105 and apply a force to the screen element 109 which is determined by the combined weight of the strip vane 181, the support member 151 and the floating piston 154 of each of the print head drive devices 147, 147.

By applying a positive fluid pressure to the first fluid holes 157, 157 or a negative fluid pressure to the second fluid holes 159, 159 of the printhead drive devices 147, 147 of the first printhead unit printing 143, the force applied by the strip blade 181 to the screen element 109 can be reduced, and, through the application of sufficient fluid pressure, the strip blade 181 can be raised separately from the screen element 109, up to the upper limit set by the second screw adjusters 175, 175 of the stop adjustment mechanism 171.

Alternatively, by applying a negative fluid pressure to the first fluid holes 157, 157 or a positive fluid pressure to the second fluid holes 159, 159 of the printhead drive devices 147, 147 of the first unit of print head 143, the force applied by the strip blade 181 to the screen element 109 can be increased.

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Thus, with the controlled application of the fluid pressure to the respective of the first fluid holes 157, 157 or the second fluid holes 159, 159 of the printhead actuator devices 147, 147 of the first print head unit 143, the strip blade 181 can apply any necessary downward force F to the screen element 109, in this embodiment in the range of 0 to about 15 N, with an accuracy of about 1%, as illustrated in Figure 6 (a), or the strip blade 181 can be kept separate from the screen element 109 in an inoperative position, as illustrated in Figure 6 (b).

In an alternative embodiment, sufficient fluid pressure may be applied to the first fluid holes 157, 157 of the first print head unit 143 to counteract the dead weight of the strip mechanism, and a controlled fluid pressure may be applied to the second fluid holes 159, 159 of the first print head unit 143 to apply a necessary downward force to the strip blade 181.

Without pressure applied to the printhead drive devices 147, 147 of the second printhead unit 145, the pistons 154, 154 of the printhead drive devices 147, 147 will be in the defined lower stop positions by the first screw adjusters 173, 173 of the stop adjustment mechanism 171, so that the counter-strip 183 is kept little separated from the screen element 109 in a re-coated position, as illustrated in Figure 6 (b).

By applying a positive fluid pressure to the second fluid holes 159, 159 or a negative fluid pressure to the first fluid holes 157, 157 of the printhead drive devices 147, 147 of the second printhead unit impression 145, the counter-strip 183 locks in the overcoat position. When liquid inks are used, the printing screen 105 commonly uses a coated mesh for the screen element 109 and it is desirable to maintain the image area of the screen element 109, as defined by the pattern of the print openings 110, covered with a thin film of ink in order to prevent the ink from drying on the screen element 109 and blocking the pattern of the print openings 110. By placing the counter-strip 183 in the re-coated position, when the assembly of the printhead 119 to the initial starting position in each return stroke, the counter-strip 183 acts to re-coat the surface of the screen element 109 with a thin film of the printing medium, as illustrated in Figure 6 (b) .

By applying a positive fluid pressure to the first fluid holes 157, 157 or a negative fluid pressure to the second fluid holes 159, 159 of the printhead drive devices 147, 147 of the second printhead unit Printing 145, the counter-strip 183 can be raised even further apart from the screen element 109, defined by the upper limit set by the second screw adjusters 175, 175 of the stop adjustment mechanism 171, as illustrated in Figure 6 (a ).

In this embodiment the impulse unit 121 comprises first and second impulse elements 185, 185, here serrated belts, which are connected to the coupling elements 142, 142 of the respective first and second carriages 141, 141, and a drive motor 187 which can function to drive the impulse elements 185, 185 and therefore the first and second carriages 141, 141. In this embodiment the impulse elements 185, 185 are commonly coupled by means of a drive shaft 189, and the drive motor 187 is coupled to an impulse element 185, so that operation of the drive motor 187 commonly drives the impulse elements 185, 185 through the drive shaft 189.

The operation of the printhead assembly 119 is illustrated in Figures 6 (a) and (b).

In a printing stroke, as illustrated in Figure 6 (a), in which the printhead assembly 119 moves in a first direction D1, the strip blade 181 of the first printhead unit 143 is in contact with the screen element 109 and loaded with a necessary downward force F by the printhead actuator devices 147, 147 of the first printhead unit 143, such as to push the printing means PM forward to the face of the strip blade 181 and through the pattern of the print openings 110 in the screen element 109 as deposits on a workpiece W that is supported beneath them, and the counter-strip 183 of the second unit of printhead 145 is held in the inoperative position raised by the printhead drive devices 147, 147 of the second printhead unit 145.

In a return stroke, as illustrated in Fig. 6 (b), in which the printhead assembly 119 moves in a second direction D2, the strip blade 181 of the first printhead unit 143 is it rises out of contact with the screen element 109 and is maintained in an inoperative position raised by the operation of the printhead actuator devices 147, 147 of the first printhead unit 143, and the counter-strip 183 of the second print head unit 145 is lowered and held in the operative position to re-coat, such as to re-coat the surface of the screen element 109 with a thin film of the printing medium PM.

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In an alternative embodiment, as illustrated in Figures 7 (a) and (b), which, for example, is for the printing of thick viscous materials, the support member 151 of the second print head unit 145 has installed a strip blade 181 instead of a counter-strip 183, and the second printhead unit 145 functions in the same manner as the first printhead unit 143, as described hereinbefore.

In this embodiment, the upper ends of the strip blades 181, 181 are spaced sufficiently to allow the introduction of PM printing media into the cavity that is defined therebetween. In this way, the cavity between the strip blades 181, 181 can be maintained with a high filling volume of PM printing medium, and at least so that the printing medium PM extends through the cavity in contact with each of the paddle blades 181, 181. With this configuration, the circulation of the printing medium PM is achieved, which allows a sufficient level of pseudoplastic behavior to allow printing at high printing speeds, and higher printing speeds than the existing printheads.

In this embodiment, the printhead assembly 119 includes first and second extreme limitations 191, 191, which are coupled to the respective ends of the strip blades 181, 181, such as to retain the impression means PM between the strip blades 181, 181.

In this embodiment, the extreme limitations 191, 191 are fixed with fasteners to the ends of the blade blades 181, 181, and each includes slotted openings, which extend in vertical orientation to allow the relative vertical movement of the blades. of strip 181, 181.

The operation of this alternative printhead assembly 119 is illustrated in Figures 7 (a) and (b). In this embodiment, the printhead assembly 119 is movable in the first and second printing races in opposite directions D1, D2.

In a first printing stroke outside, as illustrated in Figure 7 (a), in which the printhead assembly 119 moves in a first direction D1, the rear strip blade 181 of the first printhead unit Print 143 is in contact with the screen element 109 and loaded with a necessary downward force F by the print head drive devices 147, 147 of the first print head unit 143, such as to push the print media PM forward of the face of the strip blade 181 and through the pattern of the print openings 110 in the screen element 109 as deposits on a workpiece W that is supported beneath them, and the front strip blade 181 of the second printhead unit 145 is held in the raised position slightly separated from the screen element 109 by the printhead drive devices 147, 147 of the second printhead unit pressure 145. The front stripper blade 181 of the second print head unit 145 is very close to the screen element 109, but spaced sufficiently to prevent contact with the screen element 109 during the printing stroke outside. In one embodiment the lower edge of the front strip blade 181 is spaced no more than about 1 mm from the screen element 109, and preferably no more than about 0.5 mm. This configuration contrasts with the prior art strip systems, in which the front strip is kept very separate from the rear operating strip.

In a second return printing stroke, as illustrated in Figure 7 (b), in which the printhead assembly 119 moves in a second opposite direction D2, the rear stripper blade 181 of the second unit of printhead 145 is in contact with the screen element 109 and loaded with a necessary downward force F by the printhead drive devices 147, 147 of the second printhead unit 145, such as to push the medium of print PM forward of the face of the strip vane 181 and through the pattern of the print openings 110 in the screen element 109 as deposits on a workpiece W that is supported beneath them, and the blade of front strip 181 of the first printhead unit 143 is held in the raised position slightly separated from the screen element 109 by the printhead drive devices 147, 147 of the first print unit printhead 143. Similar to the configuration for the first print run outside, the front strip blade 181 of the first printhead unit 143 is very close to the screen element 109, but spaced sufficiently to prevent contact with the screen element 109 during the return printing stroke. In one embodiment the lower edge of the front strip blade 181 is spaced no more than about 1 mm from the screen element 109, and preferably no more than about 0.5 mm.

The present inventor has surprisingly established that this configuration of the strip vanes 181, 181, in which the front strip shovel 181 in the direction of movement is raised slightly separated from the screen element 109, in combination with the contribution of a volume PM print media in the cavity between the strip blades 181, 181 that substantially fills the cavity, allows for performance at least equivalent to the existing built-in screen printing heads.

Finally, it will be understood that the present invention has been described in its preferred embodiments and can be modified in many different ways without departing from the scope of the invention as defined by the appended claims.

Claims (15)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 1. A print head assembly for printing a print medium on a workpiece through a print screen (105) that includes a screen element (109) having a pattern of print openings (110) in the same, wherein the assembly comprises first and second printhead units (143, 145) that are mounted in parallel relationship adjacent to, and between, first and second carriages (141, 141), and where each of the printhead units (143, 145) comprise first and second drive devices (147, 147) of printhead that can be mounted on the respective carriages (141, 141), and a support member (151) which extends between the print head drive devices (147, 147), such as to be movable vertically therebetween, and in use supports a print element (181, 183), the support members (151) being of the printhead units (143, 145) available positions in spaced relationship, such as to allow the introduction of print media from above between them. 2. The assembly of claim 1, wherein the printhead drive devices (147, 147) of each printhead unit (143, 145) can be operated to allow a controlled downward force in the respective member of support (151), thereby allowing the application of a controlled downward force on a printing element (181, 183) when connected to the support member (151), optionally the controlled downward force is in the range of 0 at about 15 N, optionally with an accuracy of less than about 1%, optionally the printhead drive devices (147, 147) comprise low friction drive devices, optionally the drive devices (147, 147) of print head comprise low friction pneumatic drive devices, optionally each of the print head drive devices (147, 147) It comprises a cylinder (153), a floating piston (154) that is movably disposed within the cylinder (153) and includes a connecting element (155) that is connected to one end of the support member (151), and to the minus a fluid orifice (157, 159) to which fluid pressure is applied to raise or lower the floating piston (154). 3. The assembly of claim 1 or 2, wherein each of the printhead units (143, 145) further comprises vertical grids (152, 152), optionally linear supports, which the respective support member (151) ) vertically, so that substantially no horizontal force component is transmitted to the respective printhead drive devices (147, 147). 4. The assembly of any one of claims 1 to 3, wherein the support member (151) comprises a substantially U-shaped member, optionally the support member (151) defines a substantially cleared opening when viewed laterally, optionally the support member (151) includes first and second support elements (161, 161) that are coupled to the respective first and second actuation devices (147, 147) of the printhead and extend vertically adjacent to respective inner sides of the drive devices (147, 147) of the print head, and a horizontal bar element (163) extending between the opposite lower ends of the support elements (161, 161). 5. The assembly of any one of claims 1 to 4, wherein each of the printhead units (143, 145) comprises a stop adjustment mechanism (171), which allows setting upper and lower limits for movement vertical of the respective printhead drive devices (147, 147), optionally the stop adjustment mechanism (171) comprises first and second stop adjusters (173, 175), optionally screw adjusters, at each end of the member of support (151), the first stop adjusters (173, 173) establish a lower limit for the vertical movement of the respective printhead drive devices (147, 147) and the second stop adjusters (175, 175) they establish an upper limit for the vertical movement of the respective printhead drive devices (147, 147), optionally the second stop adjusters (175, 175) can be decoupled ar to allow the respective support member (151) to be raised very far from the print screen (105), thereby facilitating the removal of the print screen (105). 6. The assembly of any one of claims 1 to 5, wherein (i) the support member (151) of the first printhead unit (143) has a strip blade (181) connected thereto and the member of support (151) of the second printhead unit (145) has a counter-strip (183) connected thereto, and the assembly is movable in print and return runs directed opposite, so that, in the printing stroke, the printhead drive devices (147, 147) of the first printhead unit (143) are controlled to bring the strip blade (181) to the operative contact with the screen element (109) and apply to the same a downward force necessary for printing and the printhead drive devices (147, 147) of the second printhead unit (145) are controlled to raise the counter-strip (183) to an inoperative position, and, in the return run, the disposi The print head drive devices (147, 147) of the first print head unit (143) are controlled to raise the strip bar (181) to an inoperative position and the head drive devices (147, 147) Printing of the second printhead unit (145) are controlled to lower the countertop (183) to an operating position slightly separated from the screen element (109), such as to allow 5 10 fifteen twenty 25 30 35 40 Four. Five fifty application of a print media film on the surface of the screen element (109), or (ii) each of the support members (151) of the printhead units (143, 145) has a strip blade (181) connected thereto, and the assembly is movable in first and second printing runs directed opposite, so that, in the first printing run, the print head drive devices (147, 147) of the first unit The print head (143) is controlled to bring the strip terminal (181) connected thereto to the operative contact with the screen element (109) and apply to it a downward force necessary to print and the drive devices (147, 147) of the printhead of the second printhead unit (145) are controlled to raise the blade strip (181) connected thereto slightly separated from the screen element (109), and, in the second printing career, l The print head actuation devices (147, 147) of the first print head unit (143) are controlled to raise the strip blade (181) connected thereto to a position slightly separated from the screen element (109 ) and the printhead drive devices (147, 147) of the second printhead unit (145) are controlled to lower the strip blade (181) connected thereto to the operative contact with the display element ( 109) and apply to it a downward force necessary to print. 7. A silkscreen system, comprising: a support frame (111) that supports a printing screen (105) and includes first and second grains (117, 117), optionally the support frame (111) has a rectangular shape in plan view and includes first support elements and second (125, 125) of frame on each of the opposite sides thereof that receive and support the opposite sides of the printing screen (105); the assembly (119) of any one of claims 1 to 6 that is supported on and between the grids (117, 117), such as to be movable to print a print medium through the print screen (105) on a work piece that is supported under it; Y a pulse unit (121) to drive the assembly (119) along the grids (117, 117) in one of the first and second opposite directions. 8. A screen printing method of a print medium on a workpiece through a print screen (105) that includes a screen element (109) having a pattern of print openings (110) therein, comprising the I method the stages of: providing a printhead assembly (119) comprising: first and second carriages (141, 141) that are movably supported on the respective first and second grids (117, 117); characterized in that the printhead assembly (119) further comprises: first and second printhead units (143, 145) that are mounted in adjacent parallel relationship to and between the carriages (141, 141), wherein each of The printhead units (143, 145) comprise first and second drive devices (147, 147) of the printhead that are mounted on the respective carriages (141, 141), and a support member (151) which is extends between the printhead drive devices (147, 147), such as to be movable vertically therebetween, the support members (151) of the printhead units (143, 145) being arranged in spaced relationship ; connecting printing elements (181, 183), such as one of a strip blade (181) or a counter-strip (183), to the support members (151) of the printhead units (143, 145); introduce printing medium from above and between support members (151); Y put the assembly (119) into operation to print on a work piece that is supported under the printing screen (105). 9. The method of claim 8, wherein the printhead drive devices (147, 147) of each printhead unit (143, 145) can be operated to allow a controlled downward force in the respective member of support (151), thereby allowing the application of a controlled downward force on a printing element (109) that is connected to the support member (151), optionally the controlled downward force is in the range of about 0 to about 15 N, optionally with an accuracy of less than about 1%, optionally the printhead drive devices (147, 147) comprise low friction drive devices, optionally the printhead drive devices (147, 147) printing comprises low friction pneumatic drive devices, optionally each of the print head drive devices (147, 147) comprises a cylinder (153), a floating piston (154) that is movably disposed within the cylinder (153) and includes a connecting element (155) that connects to one end of the support member (151), and at least one fluid hole (157, 159) to which fluid pressure is applied to raise or lower the floating piston (154). 5 10 fifteen twenty 25 30 35 40 Four. Five fifty 10. The method of claim 8 or 9, wherein each of the printhead units (143, 145) further comprises vertical ranges (152, 152), optionally linear supports, which the respective support member (151) ) vertically, so that substantially no horizontal force component is transmitted to the respective printhead drive devices (147, 147). 11. The method of any of claims 8 to 10, wherein the support member (151) comprises a substantially U-shaped member, optionally the support member (151) defines a substantially detached opening when viewed laterally, optionally The support member (151) includes first and second support elements (161, 161) which are coupled to the respective of the first and second actuation devices (147, 147) of the printhead and extend vertically adjacent to respective sides interiors of the print head actuation devices (147, 147), and a horizontal bar element (163) extending between the opposite lower ends of the support elements (161, 161). 12. The method of any of claims 8 to 11, wherein each of the printhead units (143, 145) comprises a stop adjustment mechanism (171), which allows setting upper and lower limits for movement. vertical of the respective printhead drive devices (147, 147), optionally the stop adjustment mechanism (171) comprises first and second stop adjusters (173, 175), optionally screw adjusters, at each end of the member of support (151), and further comprising the stage of: adjust the first stop adjusters (173, 173) to establish a lower limit for the vertical movement of the respective print head actuator devices (147, 147) and the second stop adjusters (175, 175) to set a limit upper for the vertical movement of the respective printhead drive devices (147, 147); also optionally comprising the stage of: decouple the second stop adjusters (175, 175) to allow the respective support member (151) to be lifted very far from the print screen (105), thereby facilitating the removal of the print screen (105); which also optionally comprises the stage of: introduce print media from above and between support members (151). 13. The method of any one of claims 8 to 12, wherein the support member (151) of the first print head unit (143) has a strip blade (181) connected thereto and the support member ( 151) of the second printhead unit (145) has a counter-strip (183) connected thereto, and the operating stage of the printhead assembly comprises the steps of: control the printhead drive devices (147, 147) of the first printhead unit (143) to bring the strip blade (181) to the operative contact with the screen element (109) and apply to it a downward force necessary to print; controlling the printhead drive devices (147, 147) of the second printhead unit (145) to raise the counter-strip (183) to an inoperative position; driving the assembly (119) on the surface of the screen element (109) in a first direction to print deposits of the printing medium on the work piece that is supported under the printing screen (105); controlling the printhead drive devices (147, 147) of the first printhead unit (143) to raise the strip blade (181) to the inoperative position; controlling the printhead drive devices (147, 147) of the second printhead unit (145) to lower the counter-strip (183) to an operating position slightly separated from the screen element (109); Y propelling the assembly (119) on the surface of the screen element (109) in a second opposite direction to apply a film of printing medium on the surface of the screen element (109). 14. The method of any one of claims 8 to 12, wherein each of the support members (151) of the first and second printhead units (143, 145) has a strip blade (181) connected to the same that together define a cavity, and the operating stage of the printhead assembly comprises the stages of: 5 10 fifteen twenty 25 controlling the printhead drive devices (147, 147) of the first printhead unit (143) to bring the strip terminal (181) connected thereto to the operative contact with the display element (109) and apply to it a downward force necessary to print; controlling the printhead drive devices (147, 147) of the second printhead unit (145) to raise the strip blade (181) connected thereto slightly separated from the screen element (109); driving the assembly (119) on the surface of the screen element (109) in a first direction to print deposits of the printing medium on the work piece that is supported under the printing screen (105); controlling the printhead drive devices (147, 147) of the first printhead unit (143) to raise the strip blade (181) connected thereto to a position slightly separated from the screen element (105); control the printhead drive devices (147, 147) of the second printhead unit (145) to lower the strip blade (181) connected thereto to the operative contact with the display element (109) and apply to it a downward force necessary to print; and propelling the assembly (119) on the surface of the screen element (109) in a second opposite direction to print deposits of the printing medium on the workpiece that is supported under the printing screen (105); which also optionally comprises the stage of: maintaining the cavity between the strip blades (181) with a volume of printing medium that is such that the printing medium extends at least through the cavity in contact with each of the strip blades (181); which also optionally comprises the stage of: keep the cavity between the paddle blades (181) substantially filled with printing medium. 15. The method of any of claims 8 to 14, wherein the printing medium is a fluid material, optionally a liquid ink, or a thick viscous material, optionally a soft solder paste.